High viscosity starch derivatives



United States Patent 3,271,387 HIGH VISCOSITY STARCH DERIVATIVES Chim Patel, St. Louis, Mo., and Ronald E. Pyle, Granite City, 11]., assignors to Union Starch 8: Refining Co., Inc., Columbus, Ind., a corporation of Indiana No Drawing. Filed Oct. 10, 1962, Ser. No. 229,724 14 Claims. (Cl. 260-2335) The present invention relates generally to starch derivatives and more particularly to a novel high viscosity, water soluble starch product and to a novel method for producing it from unmodified starch. Specifically, the present invention pertains to a thick-boiling starch ester prepared from unmodified starch, using chlorothioformate esters as the principal reactants.

An object of the present invention is to produce a modified starch product which gives higher stable viscosity pastes than unmodified starch when cooked either with water or alkaline solution.

A second object of this invention is to produce a modified starch product which gelatinizes at a lower temperature than common for the unmodified starch from which it is made.

Another object is to prepare a modified starch product which yields a softer cold paste than that of the unmodified starch.

A further object of this invention is to produce a modified starch product having the above-listed properties by a method which does not disrupt the starch granules through gelatinization.

This invention is based on the discovery that the starch with various chlorothioformate compounds under the conditions specified produces modified starch products which yield higher paste viscosities than obtained from the unmodified starch.

Briefly, the objects of the present invention are attained by reacting a relatively small amount of an alkyl or aryl chlorothioformate ester with unmodified starch, under controlled conditions of .pH, and concentration of the chlorothioformate ester to produce a water soluble thickboiling starch.

The starch is preferably in the form of a slurry. The time, temperature and Baum of the starch slurry are minor variables in the reaction as disclosed below but these conditions may be varied over wide limits and are, therefore, not considered critic-a1.

An additional advantage of the process of this invention is that starch slurries are treated under conditions especially suited to equipment common to the industry.

In the following teachings of the present invention, a starch slurry, i.e., unmodified corn starch gran-ules and water at a temperature of about -55 C. and with a Baum of 14 to 21 is acidified or made alkaline to adjust the pH thereof to preferably between 4 to 10. The starting pH of the slurry is usually in the neighborhood of about 3-5 and will depend upon the source of the com, the time of the year of its harvest and conditions in the plant which produces the starch slurry. Any base or acid may be used which will adjust the pH to a suit able level, such as sodium carbonate (Na C0 hydrochloric acid or the like. It should be borne in mind that the base or acid is not used to modify the starch but to adjust the pH of the slurry prior to the addition of the reactant.

Our study of the reaction and product obtained by the process leads us to the belief that the product obtained is actually a mixed ester of carbonylrnonothio acid, CO(SH)OH, and has the formula 3,271,387 Patented Sept. 6, 1966 where X is the starch radical and R is an alkyl, alkylene, or aryl group. In accordance with this theory the reaction which takes place is a follows:

We are aware that allyl chloroformate has been proposed as an etherifying agent for starch (see U.S. 2,668,- 156). We have found, however, that the chlorothioformate is much more reactive with starch than the chloroformates and that they react with starch at close to the neutral range of pH. Obviously the resultant products are different.

The amount of chlorothioform-ate ester employed for modification may vary from 0.03% to about 1.0%, based on dry substance starch. With 0.05% of the chlorothioformate, a significant increase of hot paste viscosity in water and maximum alkaline viscosity are noted. As more of the chlorothioform-ate ester is reacted with the starch, the viscosity of the modified starch increases; the chlorothioformate esters, however, form insoluble starch when reacted at concentrations of more than 1.0% with unmodified starch. The reaction can be conducted at a pH level above about 4 and up to about pH 10. The preferred pH range is 7-9.

The reaction proceeds satisfactorily at temperatures about 20 to 45 C. Some decrease in viscosity is observed at temperatures between about 49 and 55 C. Starch slurries at about 37-45 C., as delivered to the drying equipment in starch plants, work. very satisfactorily in the process.

The reaction time is not critical. Starch sl-urries reacted from 1 to 24 hours or more before being sent to the dryers have been found to be satisfactory. Occasionally, it is not possible to dry a reacted starch immediately and the delay of 10 hours or more has not caused any change in the viscosity of the modified starch.

The starch may be treated in the form of a slurry as it comes from the final stage of the wet milling process. The slurry may have almost any density. When slurries of 14 to 21 Baum have been treated under otherwise similar conditions, the resultant viscosities and other properties of the products are substantially the same.

After treating with chlorothioformate ester, the slurries are filtered and the starch is dried at about C for example, to about 10% moisture.

The measurement of the viscosity of hot starch pastes is used in the industry to determine the degree of modification of starch products. Hot paste viscosity is commonly determined by the Scott method and the Corn Industries viscometer method. Procedures for these methods of analysis are described by R. W. Ker-r in his book entitled, Chemistry and Industry of Starch.

In addition to these tests, the maximum alkaline viscosity (MAV) was determined. In this test, grams of starch (as-is basis )is mixed with 900 ml. of water at 49 C. and 100 ml. of 32% sodium hydroxide solution.

This mixture is placed in a steam-jacketed vessel equipped with a mechanical agitator. Agitation is started and the temperature of the mixture is raised to 74 C. After holding at this temperature for 10 minutes, 900 ml. of tap water at 27 C. is added to the cooked starch paste. The mixture is cooled to 38 C. and the viscosity is measured by means of a Brookfield viscometer.

The following examples further illustrate the process of the invention.

The processes, as described below, are applied to corn starch. However, these processes are equally applicable for modifying other starches, such as potato, tapioca, rice, grain, sorghum and wheat starches.

3 EXAMPLE 1 A corn starch slurry sample of 20 Baum corrected to 155 C. was separated into two equal parts. The

4 (5) The Alkali Number of the n-octyl chlorothioformate treated starches was lower than that of the controls.

Starches with these higher viscosities are especially usefirst part was used as a control. To the second part, 5 ful for adhesives; corrugating paper; charcoal, coal and 0.03% dry substance basis (D.S.B.) of n-octyl chloroore briquetting; textile finishings such as back sizing; fillthioformate was added. The pH was adjusted to 9.0 and ing certain kinds of fabrics; Wet end addition in paper the fi y was held at (TOOTH temperature) manufacturing and in acoustic tile manufacturing. for 3 ours. Thereafter the slurry was neutralized to pH 5.0, filtered and the starch was dried at 115 C. to a EXAMPLES 8 14 10% moisture content. The control was subjected to the The influence of pH on the process set forth in Example same treatment but without the n-octyl chlorothioformate 1 was determined by treating Baum starch slurries addition. The properties of the modified and control With 0.1% D.S.B. n-octyl chlorothioformate at 2632 C. starch are set forth in Table I below. for 3 hours at pH levels of 4-10. The results are set forth Table l Conc. of n-octyl Gel Max. Vise. A.P.V., Scott M.A.V., Alkali Example Chlorothiofor- Temp, Visc., at 30, gn1.-c1n. Visc. cps. Number mate, percent C. gin-cm. gnu-cm.

Control 87 140 110 1, 400 90 1,100 8.28 0. 03 80. 0 163 140 1, 200 130 1,800 8.00

Maximum Viscosity, Viscosity at 30 Minutes and Aged in Table III and show that n-octyl chlorothioformate gives Paste Viscosity (A.P.V.) were measured in gram-centisatisfactory results in the range pH 7.010.0. Also, there meters with the Corn Industries viscometer. Maximum was some increase in viscosity between pH 4 .0 and 6.0. Alkaline Viscosity (M.A.V.) was measured in centipoises Table HI with Brookfield viscometer. Alkali Number was determined according to the procedure given by Schoch and Jensen in the Ind. Eng. Chem., Anal. Ed., 12, 531 33 9.- Gel, Max. SW (1940). Example chlorothiopH Te rnp, Visc., 30,

Treatment of starch with 0.03% n-octyl chlorothio- 32 353;? c formate measurably influenced the viscosity characteristics of the starch when pasted with water and also with 0 8&0 140 110 alkaline solution. 8 8-} g-g 23-3 EXAMPLES M 8 1 9 3 as a a The process set forth in Example 1 was repeated with 1 230 190 ODS-1.0% concentrations of n-octyl chlorothioformate 8-8 21- 533 328 to determine the influence of the concentration of this reactant on the properties of the final product. The properties of the modified starch products (Examples 2-7) and of the unmodified controls for these samples are EXAMPLES 15-19 Examples 15-19 were conducted substantially as Expresented in Table II. 40 ample 1 on a 20 Baum starch slurry with 0.1% D.S.B.

Table II 00110. of n-octyl Gel Max. Vise. A.P.V., M.A.V., Alkali Scott Example Chlorothiofor- Temp, Visc., at 30, gm.-cm. eps. Number Vise.

mate, percent C. gm.-cm. gnL-cm.

It will be seen from the above table that the following modifications in viscosity properties have occurred:

(1) The gelatinization temperature was lowered 13 C. below that of the control samples. The gelatinization temperature reached a minimum in sample treated with 0.2% n-octyl chlorothioformate.

(2) In all cases, the maximum viscosity of the hot pastes was increased, reaching its greatest value at the 0.2% n-octyl chlorothioformate treatment level. Insoluble starch forms when unmodified starch reacted with more than 1.0% n-octyl chlorothioformate.

(3) Set back on cooling as measured by the Aged Paste Viscosity (A.P.V.) was significantly lowered. Maximum lowering of this property was reached at 0.2% n-octyl chlorothiofor mate treatment level.

(4) The Maximum Alkali Viscosity was much higher than the controls at all levels of treatment.

n-octyl chlorothioformate at a pH of 9.0 for 3 hours and at various temperatures as indicated in Table IV. The data obtained indicate that temperature ranges from 26-55 C. give satisfactory results although somewhat lower viscosity at higher reaction temperature.

Table IV Temp., Gel. Max. Visc., Visc. at 30 Example 0. Temp, O. gn1.-cm. min.,

gm.-ern.

Controls (15-19) 87 135 15 26 85 240 180 38 85 210 170 43 .85 195 102 49 84 178 55 84 125 The process has also been conducted at various reaction times but no significant differences in results have been noted between about 1 to over 24 hours of reaction time. Similarly, changing the Baum of the slurry has been found to have no significant eifect on the results.

9. The starch derivative as claimed in claim 14 wherein R is an n-ethyl radical.

10. The starch derivative as claimed in claim 14 Wherein R is a phenyl radical.

11. The starch derivative as claimed in claim 14 wherein R is a dodecyl radical. EXAMPLES 20 24 12. The starch derivative as claimed in claim 14 where- Examples 20-24 were conducted substantially as Exin R is a propyl radical. ample 1 on a 20 Baum starch slurry with 0.1% D.S.B. 13. A process for preparing a high viscosity, water of various chlorothioformate compounds (ethyl, methyl, 1O Soluble starch derivative comprising phenyl, dodecyl, n-propyl) for 3 hours at pH 9,0 d t providing an aqueous slurry of substantially unmodified room temperature (2632 C.). The analyses indicate Starch having a P 0f about 1 that they all (Examples 24) give the same result 'as adding from about 0.03 to about 0.3%, based on the n-octyl chlorothioformate. dry starch, of a chlorothiofor-mate ester of an alcohol Table V Gel. Max. Vise. Example Chlorothioformate Temp, Visc., at 30 Scott 0. gm.- mm, Vise.

Cm. gm.-cm.

ifffiiift'iith: iii 11aaaiaraaiiaroinraiiij: 3213 ii; 133 1% Methyl chlor0thioformate- 85. 5 170 130 142 Phenyl chlorothioiormate... 87.0 155 140 140 Dodecyl chlorothioformate 85.0 180 146 152 n-Propylchlorothioformate. 84. 0 164 150 138 The features and principles underlying the invention Selected from the group Consisting of l yl alC described above in connection with specific exemplificaof 1-12 carbon atoms and phenyl alcohol, tions will suggest to those skilled in the art many other maintaining file mixture atab0l1t2655c a Period modifications thereof. It is accordingly desired that the 30 of at least 1 hour, and appended claims shall not be limited to any specific feal'ecovbfing the modified Starch om e mixture. ture or detail thereof, 14. As a high viscosity starch derivative, the reaction W l i product obtained by reacting starch with about 0.03 to 1. The process as claimed in claim 13 wherein the about based on The dry starch, of a ChlOfOtbiO- chlorothioformate ester is the n-octyl ester thereof. formale ester of all 31001101 Selected from the group C011- 2. The process as claimed in claim 13 wherein the sisting of alkyl alcohols 0f carbon atbms and p y chlorothioformate st i th methyl t alcohol, the reaction being carried out at a pH of 7-10 3. The process as claimed in claim 13 wherein the and atatempefatufe of chlorothioformate ester is the ethyl ester.

4. The process as claimed in claim 13 wherein the References Clted by the Exammer chlorothioformate ester is the phenyl ester. UNITED STATES PATENTS 5. The process as claimed in claim 13 wherein the 2,668,156 2/1954 Caldwell 26O 2333 X chlorothioformate ester is the dodecyl ester. 2,863,899 12/1958 Harris 260455 6. The process as claimed in claim 13 Wherem the chlorothioformate ester is the propyl ester.

7. The starch derivative as claimed in claim 14 wherein R is an n-octyl radical.

8. The starch derivative as claimed in claim 14 wherein R is a methyl radical.

LEON I. BERCOVITZ, Primary Examiner.

WILLIAM H. SHORT, Examiner.

E. C. EDWARDS, R. W. MULCAHY,

Assistant Examiners. 

14. AS A HIGH VISCOSITY STARCH DERIVATIVE, THE REACTION PRODUCT OBTAINED BY REACTING STARCH WITH ABOUT 0.03 TO ABOUT 0.3%, BASED ON THE DRY STARCH, OF A CHLOROTHIOFORMATE ESTER OF AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF ALKYL ALCOHOLS OF 1-12 CARBON ATOMS AND PHENYL ALCOHOL, THE REACTION BEING CARRIED OUT AT A PH OF 7-10 AND AT A TEMPERATURE OF 26-55* C. 